In recent years, a demand to an environment friendly liquid fuel with less sulfur components and aromatic hydrocarbons has been rapidly enhanced. Various studies have been carried out by fuel oil manufacturers to provide processes for producing an environment friendly liquid fuel. Among others, a process wherein a paraffinic hydrocarbon such as wax is converted to an environment friendly liquid fuel by hydrocracking in the presence of a catalyst has been studied as one measure.
It is particularly important in a process for hydrocracking a paraffinic hydrocarbon to produce a useful middle fraction at high yields with the objective of improving the economical efficiency of the process. Furthermore, the resulting fuel base material (the middle fraction) is importantly low in pour point. That is, the development of a highly efficient hydrocracking catalyst which is high in cracking activity and middle fraction yield and can provide the resulting fuel base material (the middle fraction) with a low pour point holds the key to improve the economical efficiency of the process.
Hydrocracking of vacuum gas oil has been already commercialized and is an established technique which has been used for some decades. However, since the reactivity of a paraffinic hydrocarbon mainly composed of n-paraffin is significantly different from that of a vacuum gas oil, it is difficult to divert a catalyst therefor to hydrocrack the paraffinic hydrocarbon. Therefore, research and development have been vigorously continued to achieve the development of highly efficient catalyst for hydrocracking a paraffinic hydrocarbon. Although very few, there are some patents and reports concerning such studies. For example, Patent Document 1 below discloses a catalyst comprising a support containing silica-alumina, and platinum supported thereon. In Patent Document 2, there is an example of study wherein a paraffinic hydrocarbon was hydrocracked using a catalyst comprising platinum supported on a USY zeolite.
In general, zeolite has a satisfactory level of cracking activity but has deficiencies that it is low in middle fraction yield and fails to provide the resulting fuel base material (the middle fraction) with a sufficient low pour point. On the other hand, an amorphous solid acid catalyst a typical example of which is silica-alumina is in a satisfactorily high level in terms of middle fraction yield and fuel base material (the middle fraction) pour point but is low in cracking activity. That is, a catalyst satisfying all the requirements of high cracking activity, high middle fraction yield, and low pour point of fuel base material (the middle fraction) has not been developed yet, resulting in a serious obstacle to improve the economical efficiency of a process for hydrocracking a paraffinic hydrocarbon.                (1) Japanese Patent Laid-Open Publication No. 6-41549        (2) Japanese Patent Laid-Open Publication No. 2004-255241        